The subject of the present invention is a device for the nondestructive recording of a rotational movement on the surface of a specimen, a test unit which comprises such a device, as well as a method for the nondestructive recording of a rotational movement of a device on the surface of a specimen.
Particularly in the field of nondestructive material testing, for example by means of ultrasound or by means of eddy currents, a wide range of methods and devices are known from the prior art, with the aid of which it is possible to record structural characteristics of a specimen which for example can relate to the volume of the specimen or also to surfaces of the specimen and can for example pertain to imperfections, cracks, cavities, corroded surfaces, etc. Generally, the devices used for such testing purposes are based on suitable transmission and receiver units in the form of a probe assembly which generate test signals which are detected after an interaction with the specimen. The structure of the specimen in the spatial region investigated can then be deduced from the echo signals detected. If one displaces the probe assembly on the surface of the specimen during the testing method and records the structural characteristics of the specimen during the displacement in dependence on the probe position, then it is possible to create a spatial image of the interesting structural characteristics of the specimen.
The methods and devices used today to some extent achieve extraordinary accuracies when resolving the structural characteristics of the specimen investigated. However, the resolution achieved during the following of the movement of the probe on the surface remains far behind the resolution capability of the structure sensitive investigation methods used, such as e.g. an ultrasound pulse-echo method, in the vast majority of cases. This is due to the fact that until today only mechanical displacement transducers are used in practice for recording the movement of the probe on the surface of the specimen. Due to the principle used, these are affected with a relatively high measurement error. Furthermore, no systems have become known for a long time which would allow the recording of a rotational movement of the probe on the surface of the specimen.